In its third year at the West Side's Union Park, the Pitchfork Music Festival, a weekendlong celebration of the cutting edge in indie rock, hip-hop and electronic dance music, firmly established itself as a model for how a great urban music fest should be run.

Over the weekend, a total of 47,000 fans, many from across the country, enjoyed more than four dozen challenging and rewarding performances in a sublime setting with generally excellent sound and an inspiring communal vibe. (Although the park could accommodate more, promoters sold out to preset capacities of 17,000 per day Saturday and Sunday and 13,000 Friday night to ensure a comfortable experience.)

Among the attendees: 250 journalists who came from as far as New York, Los Angeles and London to catch a first glimpse of artists pegged as "next big things" by the influential Chicago-based Webzine, PitchforkMedia.com. In fact, the greatest testament to the site's power in breaking new acts was the cause of the fest's biggest glitches: Dan Deacon, an electronic performer from Baltimore, and Girl Talk, a k a DJ Gregg Gillis, drew massive crowds that swamped the smaller third stage, exceeding capacity and forcing the Chicago Fire Department to cut those performances short.

Pitchfork should consider keeping all of the acts on the main stages during year four. If promoters don't compromise on the eclecticism of the bookings, the festival will only be better for it, in a league with the legendary '60s fests like Monterey Pop.

After a volume problem that plagued Slint's show on Friday -- resolved when a new sound system was brought up from Champaign and installed overnight -- performances on the two main stages in the center of the park went off without a hitch, and some ranked with the best live-music moments I've ever had. Chief among them: a rare live appearance by 74-year-old rock legend Yoko Ono, who headlined Saturday.

Ono has become an icon to underground music fans who couldn't care less about whether she helped break up the Beatles; they love her because she's an unapologetic hell-raiser and musical innovator. Backed by an accomplished band and joined for a cameo by Sonic Youth guitarist Thurston Moore, Ono made clear her pre-John Lennon roots in the classical avant-garde (with John Cage and La Monte Young) and free jazz (with Ornette Coleman), as well as conjuring the underrated noise-rock of the Plastic Ono Band in the early '70s, all the while sounding utterly fresh and of the moment.

By no means is Ono's voice easy on the ears, but she's a great singer nonetheless for the way her shrieks, squeals and howls twist around the grooves and melodies in the manner of a brilliant improvisational horn player. She played with as much energy as any musician who took the stage, and she took more chances than most, closing Saturday's lineup with an inspiring and historic experience as the crowd joined her in repeatedly screaming, "War is over if you want it," while the park was illuminated by thousands of flashlights distributed before her show.

Other Saturday standouts included:

•    •    Atlanta's Mastodon, which stripped away much of mainstream metal's frills and flash to deliver an unrelentingly heavy set that at first startled the well-behaved indie-rockers, though they soon caught the head-banging spirit.

•    •    Virginia Beach brothers Terrence and Gene Thornton, a k a Pusha T and Malice of hip-hop duo the Clipse, who kept things simple and old-school -- just two turntables and two microphones -- but carried the crowd from their very first rhymes, using call-and-response chants to maximum effect.

•    •    The Twilight Sad, a quartet from Glasgow, Scotland, that added a pummeling rhythmic undertow to its spacey melodies, evoking mighty early '90s shoegazers Ride.

•    •    And the Chicago band Califone, which adorned its unique and atmospheric mix of Chicago blues, folk, punk and power-pop with a killer four-piece horn section.

Sunday's acts didn't have quite as much star power, but there were still plenty of great moments during the third and final long day of underground sounds. Timed to begin as worshippers were filing out of the last Sunday service at the First Baptist Church across Ashland Avenue, things kicked off with Deerhunter, a swirling space-rock/ambient punk quintet from Atlanta.

Led by flamboyantly theatrical frontman Bradford Cox, who dressed for the occasion in a sheer, sparkly white dress and whose stage presence was all the more remarkable for the fact that he suffers from Marfan Syndrome (a connective tissue disease that causes elongated limbs), the group used its succinct but sublime half-hour set to transport listeners to the dark side of the moon with a great, swirling vortex of psychedelic noise.

Other stellar turns came courtesy of Menomena, a Portland trio whose jagged, angular dance-rock created a goofy, good-time vibe worthy of Dr. Teeth and the Electric Mayhem; the Hamilton, Ontario, duo Junior Boys, who rode a much mellower electronic dance-rock groove for the perfect mid-afternoon chill-out, and Chicago's Sea and Cake, which emphasized the bottom end so often missing on record, thereby bringing a welcome heft to its wispy, summertime pop songs.

Later, England's one-man band Jamie Lidell took the stage with his mix of vintage '70s soul and electronic loops, transcending "track act" status with his explosive energy and charisma, while the young hip-hop duo the Cool Kids justified a growing buzz as Chicago's next big national breakout with spirited, upbeat rhymes churned out over old-school beats.

Finally, the festival closed with exuberant performances by Vancouver's power-pop collective the New Pornographers and New York's pioneering and endlessly creative "Daisy Age" rappers De La Soul. The former suffered a bit for missing sometimes members Dan Bejar and Neko Case, but the latter was memorably joined by Prince Paul, the legendary DJ and producer Paul Huston, who recorded the group's classic debut, "3 Feet High and Rising."

Eighteen years after that release, De La Soul in concert is still a wonderfully celebratory and life-affirming event -- as good as live hip-hop gets.

In the end, with the third Pitchfork fest standing as an unqualified artistic success as well as a profitable business venture (according to the promoters, who declined to say exactly how much money they made), the question it raised was not how it could offer so much for so little ($50 for a three-day pass), but how larger, much better-funded and more heavily hyped fests -- chief among them the reinvented Lollapalooza -- can justify charging so much while delivering far inferior sound and sight lines, milking concertgoers with overpriced amenities and assaulting them with corporate promotional hucksterism at the expense of what mattered most in Union Park: the music.

In one of several community outreach programs, the promoters of the Pitchfork Music Festival invited students from the Chicago Public Schools to attend a panel featuring local music journalists on Saturday morning, then cover the festival as professionals would. The Sun-Times invited several of these students to submit critiques of their favorite performances.

Gillis, being the super-cool guy he is, invited fellow Pitchfork artists (members of Grizzly Bear, Beach House and Deerhunter) and staff to help him perform by dancing onstage and throwing confetti at audience members. It was an anarchy of good times, with Silly String, strip dancing, glow sticks, uncontrollable cavorting and very, very good music -- by far one of the best performances of the evening.

Roz Johanek, 19
University of Stirling, Scotland

At the end, Grizzly Bear's combination of chunky guitars, instruments and diverse rhythms did a fine job of translating their 2006 album "Yellow House" to the stage.

Sima Cunningham, 17
Whitney Young High School

Skylar Dees, 17
North Lawndale College Prep

The stage lights turn on and she sings. She moans, cries, shrieks, then finishes with an undulating whine. But what the audience can't grasp is that this is how she expresses true pain.

Halfway through the first song, bits and pieces of the crowd leave. Another thirty seconds pass by and there are lines of people trying to get away from her, saying things like, "This woman is crazy!" They shamelessly mock her singing.

It's possible that there has never been a more intolerant and close-minded audience, and I feel physically racked with sorrow.